What Is Matter? States of Matter
In 2013, NASA's Cassini spacecraft measured plasma surrounding Saturn's rings — a fourth state of matter existing roughly 1.4 billion km from Earth, and proof that "stuff" comes in far stranger forms than solid, liquid or gas.
Printable Worksheets
Print or save as PDF — or build a custom worksheet from any module's questions.
Q1 · List three things you can see right now that are solids, three that are liquids, and three that are gases. (Tip: gases are tricky — they're usually invisible.)
Q2 · A helium balloon floats upwards. Is helium "matter"? Does it have weight? Try to explain how something can have weight but still float.
● Know
- The scientific definition of matter (mass + volume)
- The properties of solids, liquids and gases
- That plasma is a fourth state of matter
● Understand
- Why air counts as matter even though you can't see it
- The difference between mass and weight
- Why gases spread to fill any container
● Can do
- Classify everyday objects as solid, liquid or gas
- Use the words mass and volume correctly
- Give an example of plasma in nature
- Matter
- Mass
- Volume
- Weight
- Plasma
- How much space something takes up
- A super-hot fourth state of matter (Sun, lightning)
- Anything with mass and volume
- The amount of stuff in an object (g/kg)
- The pull of gravity on an object
Hold a full water bottle in one hand and an empty one in the other — the full bottle pushes down harder. That extra push tells you the water inside has mass and takes up space. Those two facts are exactly what scientists mean by matter. The rule has two parts:
- Does it have mass? — Can you weigh it on a scale? An empty drink bottle has a mass; an idea or a shadow does not.
- Does it have volume? — Does it take up space? Even air takes up space — that's why a balloon inflates.
If the answer to both is yes, it is matter. Water, your shoe, sand, oxygen gas, even the smoke from a candle — all matter.
Things that are not matter: light, sound, heat, gravity, time. These are forms of energy or ideas. They don't sit on scales and they don't fill a measuring cup.
Try the air-in-a-balloon test: weigh an uninflated balloon on a sensitive scale, then weigh it again after you've blown it up. The second reading is higher. Air has mass.
Matter usually shows up in one of three states. The state depends on how tightly the stuff is held together.
| State | Shape | Volume | Everyday examples |
|---|---|---|---|
| Solid | Fixed (keeps its shape) | Fixed | Ice cube, school desk, rock, steel ruler |
| Liquid | Takes the shape of its container | Fixed | Water, milk, eucalyptus oil, honey |
| Gas | No fixed shape | No fixed volume — fills any container | Air, helium in a balloon, steam, the smell of toast |
A handy memory trick: a solid keeps its shape; a liquid keeps its volume but not its shape; a gas keeps neither — it spreads out to fill whatever it's in.
That's why a milk spill makes a flat puddle (liquid) but the smell of the milk drifts across the whole room (gas).
A has a fixed shape and a fixed volume. A has a fixed volume but takes the shape of its container. A has no fixed shape and no fixed volume — it fills the whole space it is in.
Wrong: "Air isn't really matter — it's nothing." Air feels like nothing because it's so spread out, but it has mass (about 1.2 g per litre at sea level) and it fills space. That's why wind can knock you over.
Right: Air is matter. A 1 litre bottle full of air weighs about 1.2 g more than a vacuum-pumped bottle. Tiny, but real.
Wrong: "Sand and powder must be liquids because you can pour them." Pouring is a behaviour, not a state. Each tiny grain of sand is still a solid — it has a fixed shape. A pile of solids can flow like a liquid without being one.
Right: Sand is a solid (made of lots of tiny solid grains). Whether something pours doesn't decide its state — fixed shape does.
Wrong: "Mass and weight are the same thing." They feel the same on Earth, but they aren't. Mass is how much stuff you've got. Weight is the pull of gravity on that stuff. On the Moon your mass is the same, but you weigh about a sixth as much.
Right: Mass (kg) stays the same anywhere. Weight (N) depends on gravity and changes between planets.
Heat a gas up enough and something weird happens — the atoms start losing their electrons. You end up with a glowing, electrically charged "soup" called plasma. It still has mass and volume, so it's matter, but it doesn't behave like a normal gas.
- The Sun and every other star is made almost entirely of plasma.
- A lightning bolt is a tube of plasma — that's why it glows.
- Neon signs, fluorescent tubes and even your TV (older plasma screens) used plasma to make light.
- The Aurora Australis (southern lights) is plasma created when the Sun's particles hit Earth's atmosphere.
Plasma is actually the most common state of matter in the universe — over 99% of all matter we can see is plasma, because stars are made of it. We just don't see much plasma on Earth because our planet isn't hot enough.
You'll hear people say "I weigh 60 kilograms". In everyday talk that's fine, but in science it's wrong. Kilograms measure mass, not weight.
| Mass | Weight | |
|---|---|---|
| What it measures | How much matter is in something | The pull of gravity on that matter |
| Units | grams (g), kilograms (kg) | newtons (N) |
| On the Moon | Same as on Earth | About 1/6 of your Earth weight |
| In space (no gravity) | Same as on Earth | Zero — you are weightless |
A 60 kg student weighs about 600 N on Earth, about 100 N on the Moon, and 0 N floating in deep space. But in every case their mass is still 60 kg — the amount of stuff hasn't changed.
You boil a kettle and a white "cloud" pours out of the spout. Predict: is that white cloud a gas, a liquid, or a mix? Explain in one sentence, then reveal.
How close was your prediction?
Nice — you noticed that "visible" usually means liquid droplets, not gas.
Great surprise to learn — real gases are usually invisible. Clouds are liquid drops.
Earlier you were asked: A helium balloon floats upwards. Is helium "matter"? How can something float if it has weight?
Now that you've worked through the lesson, write a fuller answer. Use the words mass, volume and matter at least once each.
Q1. Define the term "matter". Give one example of matter that is hard to see, and one thing from everyday life that is NOT matter. (3 marks)
Q2. A glass of water, a steel spoon, the air in a balloon and the smoke from a candle are all matter. Sort each one as solid, liquid or gas, and give the reason in terms of shape and volume. (4 marks)
Q3. A student says: "My weight is 50 kilograms and it would be the same on the Moon." Evaluate this statement. Identify two science mistakes and explain what is actually true about mass and weight on Earth vs the Moon. (4 marks)
Answers
▾MCQ 1
C — Matter must have BOTH mass and volume. A and D fail because invisible gases (air, helium) still count; B confuses matter with life.
MCQ 2
A — Both liquids and gases take the shape of their container. Liquids keep a fixed volume; gases do not.
MCQ 3
D — Light is energy, not matter. The other three are matter (a gas, a liquid and a solid).
MCQ 4
B — Mass is the amount of stuff, which doesn't change. Weight is the gravity pull on that stuff and it does change between Earth and the Moon.
MCQ 5
C — Lightning is a glowing tube of plasma. Boiling water (liquid → gas) and ice (solid) are not plasma; air at room temperature is a gas, not plasma.
Short Answer 1
Model answer: Matter is anything that has mass and takes up space (volume). An example of hard-to-see matter is air (or any gas) — it's invisible but it still has mass and fills space. Something that is NOT matter is light (or sound, heat, gravity) — these are forms of energy and do not have mass or volume.
Short Answer 2
Model answer: Glass of water = liquid (fixed volume, takes the shape of the glass). Steel spoon = solid (fixed shape and fixed volume). Air in a balloon = gas (no fixed shape — it fills the balloon — and no fixed volume; if the balloon pops it spreads out). Smoke from a candle = gas (no fixed shape, spreads to fill the room).
Short Answer 3
Model answer: Mistake 1: kilograms measure mass, not weight. Weight is measured in newtons. The student should say "my mass is 50 kg". Mistake 2: mass and weight aren't the same on the Moon. The student's mass would still be 50 kg on the Moon (the amount of stuff in them hasn't changed), but their weight would be about one-sixth — roughly 80 N instead of 500 N on Earth — because the Moon's gravity is weaker. So mass stays the same, weight changes.